How to Make a Radial Piston Water Pump

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How to make a Radial Piston Water Pumpby TeamDolphin on February 27, 2014

Table of Contents

How to make a Radial Piston Water Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro: How to make a Radial Piston Water Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1: Construct the Crank and Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 2: Pistons and Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 3: Mounting Board and Hoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 4: Gearing and Drive system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Step 5: You're done! Go pump some water! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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Intro: How to make a Radial Piston Water Pump

For a project ("Hydro do that?") at the Glasgow School of Art, our group of students was tasked with designing and manufacturing a water pump. The task was to be acompetition betwixt several teams, each taking the name of an aquatic creature. Our designated company was 'Dolphin '. The winners of the competition were to be thegroup whose pump had the highest efficiency, and the pumps had to be able to pump five liters of water, through a height of 60cm (2 feet) in less that five minutes .Our research and development led us to find that a piston pump would be the most effective way of pumping water.

We made three pump prototypes, to see which would be most effective at pumping water.We built an axial impeller, a diaphragm pump and a piston pump.

The piston pump seemed to be the most viable solution to the efficiency problem, and our online research agreed with this, so we decided to build our final design in theform of a piston pump.

However, our brief required that we do testing and optimization for the pump, so we designed our pump to have three removable and interchangeable cylinders, to allowus to test the efficiency for different numbers of cylinders.

Materials Used:

2mm aluminium sheet12mm plywood3mm acrylic sheet4mm mild steel rod4x12x4mm bearings24V, 5600 RPM electric motorClear plastic pipe (unknown origin)Aluminium BarPVC pipe T-JointsPVC plumbing pipeEvian bottle necks and capsAssorted screws, bolts, washershot gluepipe cementPlastic Weld (Dichloromethane)Reccomended Equipment:

Band saw (metal)Band saw (wood)Metal FileSandpaper (various grit)Metalwork LathePillar DrillCordless DrillAssorted drill bits (including forstner / flat bits)hot glue gun

Yeah, we used a lot of stuff on this project. The art school has a very well equipped workshop. One could probably substitute our pistons for something a bit moreaccessible, perhaps plastic and a standardized pipe size in order to make the whole task a bit less demanding in terms of equipment.

Image Notes1. Water outlets - These were the necks of plastic bottles. The pipes were attached to the bottle lids, and this made a nice interchangeable coupling system, allowingeasy pipe attachment.

All our prototypes featured this, and as such we maintained backwards compatibility throughout the project, allowing us to re-use hoses.2. Every team had to use the same motor type. 24v, 5600rpm.

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Step 1: Construct the Crank and ValvesCrank:

We started the build by constructing the master/slave crank rod assembly. This was made out of aluminium sheet. Two slave rods were cut, a master rod (which wasessentially the slave rod, but with a larger circle on one end of it), and a spacer plate. The spacer plate and the circle were to form the central hub of the crankarrangement. Each part had a 12mm hole drilled in the middle, and six smaller holes drilled around it, equally spaced to take the bolts that held the slave rods, and thewhole assembly together.

The plates were spaced out by having an extra nut on the bolts in between the two plates.

Attaching the crank shaft was a bit of a fouter, as the crank had to be bent out of 4mm mild steel rod, but it had to be bent with the crank rod assembly already on it.It was possible to bend one side first, then slide the crank rod assembly onto the shaft. Through use of a steel box-section jig, we were able to bend the other half of thecrank and make it line up. The stroke on the pistons was 50mm, so the crank had to be offset by 25mm.

Valves:

The two-part flapper valves were designed to fit the bottle caps we were using as the pipe attachment system. Since we needed all the valves to be the same, we hadthem laser cut from 3mm acrylic, and 0.5mm styrene.

We took measurements from the PVC T-joints, to make sure that we would laser cut the adapter pieces with the right inside diameter.The valves worked by having two hinged semicircular flapper plated, hinged across the diameter of the pipe. The original valves had to be replaced because of a glitchwhereby the two plated (sharing the same hinge hole) would overlap. This was solved by placing a strip between them, and stopping them overlapping.

Image Notes1. The crank was bent out of 4mm mild steel. This was tricky, as it had to bebent while the crank arrangement was on the shaft.2. 12mm wide bearings were epoxied into the centers of both the master rodand the spacer plate.3. The master rod forms one half of the whole hub.

Image Notes1. Master Rod2. Slave Rod3. Slave Rod4. The circular spacer plate sits over the round part of the master rod, and thebolts hold the slave rods in place.

Image Notes1. The V2 version of the valves had to have a thin vertical bit of styrene betweenthe two flaps to stop them overlapping one another and allowing backwards flow.

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Image Notes1. This was the remains of the steel box section jig that was used to bend thecrankshaft. Due to the way the jig was made, we had to cut it open in order toextract the whole assembly after bending.

2. Bottle top connections

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Image Notes1. The flaps fit inside the valve assembly, and were cut out of 0.5mm styrene

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Image Notes1. This piece went on the inlet side of the valve. The flaps rest on it when they'reclosed - hence the slightly smaller inside diameter.2. This piece went on the outlet side of the valve. The bar across the middlestopped the opened valve flaps falling over, or changing sides. The small Yshaped piece inside it was never used.3. This was the central piece of the lamination. This held the two flaps in place,and they hinged on the small protrusions on either side. You can see the outlineof the flaps inside the hole, showing where they fit. All of this was laser cut from3mm acrylic.

Step 2: Pistons and CylindersPistons:

The pistons were machined out of aluminium bar that just so happened to be the correct size for our cylinders.They had a groove put in them 5mm from the front end, to take the rubber O-ring that would seal the piston. As well as this, they had a large hole bored in the oppositeend to take the piston rod, and gudgeon pin (wrist pin).These were machined by putting a large-ish section of bar in the lathe, facing the end off, boring the hole for the piston rod, then using a parting off tool to cut the O-ringgroove, and then finally parting off the finished piston from the section of bar. This was done thrice to produce the piston heads that were required.

These piston heads were taken to a pillar drill, where the hole for the 4mm gudgeon pin was marked and drilled.

Cylinders:

The clear plastic we used for the cylinders was scavenged, and as such we can't advise you on where to get it. You could substitute with acrylic tube.

It so happened that the tube we used fit perfectly over the PVC T-joints, so we used pipe cement to stick them on and provide an airtight seal.

Image Notes1. 4mm gudgeon pin (wrist pin) in the hole that was bored into the end of thepiston.2. O-ring in the groove that was cut. Make sure that all three (or more) grooves areturned to the same diameter or else you may encounter piston sealing problems.3. Hole for gudgeon pin drilled in the pillar drill.

Image Notes1. Joint was attached with pipe cement.

Step 3: Mounting Board and HosesMounting Board:

This was cut out of 12mm ply. The center was marked to allow for the full 50mm stroke of the pistons plus the length of the piston rod. Six holes were marked out wherethe T-joint on the cylinder assembly would pass through the baseboard. These were cut with a forstner bit, although a flat bit would work just as well.A circular piece of ply was also cut to hold the crankshaft and support the gearbox. This piece and the baseboard were marked to have 6 holes cut in them, which hadlong bolts going through them, with PVC pipe spacers.It might have been an idea to use thinner pipe, as it turned out that the crank system hit off them ever so slightly (this was easily fixed by filing the piston rods slightlysmaller in places).It was important to note that the heads of the bolts were on the underside of the baseboard, as the addition of the gearbox later would make them inaccessible, and wouldmake it impossible to convert the rig to 2 cylinder operation.

Three guides were made with brackets to hold the cylinders straight. The brackets were strips of aluminium screwed onto the guide, and the guides were just bolted tothe baseboard to be removable.

Hoses:

These were simply hose section hot glued into holes cut into the bottle tops.The holes were cut first, then the hose inserted, then hot glue added.

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Image Notes1. these were the valve assemblies, ready to be fitted onto the inlets and outletsof the T-joints.2. The T-joints fit through the baseboard, pumping water from the underside tothe topside.

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Image Notes1. With the valve assembly on , the T-join cannot be removed. This wasremedied by cutting a channel in the baseboard, leading to a larger hole thatwould allow the valve and cylinder assembly to be removed.

Image Notes1. We marked six holes in the baseboard and on the upper board, and drilledthem. Bolts go through both boards, and the boards are spaced out with PVCpiping.2. These channels allow the cylinder valve assemblies to be removed.

Image Notes1. if you look closely, you can see that the pvc pipes were set into the twowooden boards by about 2mm. This was done with a forstner bit (again a flat bitwould work).2. 12mm holes were cut in the centers of both boards, to fit the bearings that

Image Notes1. We will cover the assembly of the gearbox and motor mount in the next fewsteps.2. These guides had clamps on them to prevent the cylinders shifting from sideto side whilst the pump is running. The clamp was made of aluminium sheet and

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held the crankshaft in place. screwed to the guide, and the guides were simply bolted to the baseboard so asto be removable.3. The hoses were hot-glued into a hose-sized hole cut into the top of the bottlelids.

Step 4: Gearing and Drive systemGearbox:

The gearbox was originally at a ratio of 100:1, providing 10Nm of torque based on the motors torque rating (it was later changed, as the device wasn't running fastenough).The gears were designed in a gear generation program, and ported into Adobe Illustrator, in which we also created the pattern for each gearbox layer. We laser cut thepattern and double layered the gears so that they could take higher torque than a single 3mm layer of acrylic. To attach them to the 4mm mild steel shafts, we drilled a1.5mm hole in the shaft, and put a pin through it and the gear, which allowed them to sustain high torque. The motor gear was simply push fit onto the motor shaft.

The motor was screwed onto the gearbox with two screws, and the whole thing was glued together with plastic weld, or dichloromethane.

Remember not to get your fingers caught in a gear system, as 10Nm of torque really hurts.

Flywheel:

As an afterthought, we added a flywheel to our pump, to smooth out the reciprocating motion and increase efficiency.This was made by taking a circular piece of plywood, marking out six points on the edge, boring large holes halfway through, and drilling small holes all the way through.

Large (15mm thick) steel slugs cut from wide steeel bar were bolted on into the holes. This will give the flywheel a large moment of inertia and smooth out the motion ofthe pump. Be careful with these flywheels, as storing a lot of energy in rotation can go wrong if there is a jam in the machine, or it suddenly stops.Under no circumstances try to stop a flywheel with your hand. One of our group members cut their hand trying this, and trust us, it's not a fun thing.

Image Notes1. you can about see the pin that was put through the shaft and gear to allow itto sustain high torque loads.2. We were able to cut the spacers to suit what we needed them for.3. The bolts that held the circular bit of plywood to the base were also able tohold the gearbox down.

Image Notes1. The gears were generated in a gear generation program, then ported via PDFinto Adobe Illustrator, so that we could cut the gearbox all at once. We cut thistemplate twice, and double layered the main gears, so that they could take thehigh torque.2. 10 tooth gear. 3mm hole in it for the motor shaft.3. 100 tooth gear4. Using the RS components website where the motors were bought from, weused their technical drawings of the motor to cut the holes for the mount. These fitperfectly!5. Gearbox spacers to set the distance between gearbox layers.6. The hole for the shaft had a slot cut in it. The shaft had a hole drilled, with a pinthrough it, to allow the shaft to mechanically grip the gear wheel.

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Image Notes1. The flywheel was a circle of plywood, with holes bored halfway through toseat some steel slugs, that were bolted on.

Step 5: You're done! Go pump some water!We thoroughly enjoyed building this water pump, and we hope you've enjoyed this tutorial, brought to you by Dolphin Dynamics.Here you can see some of the prototypes we worked on before arriving at the final product.

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Image Notes1. Prototype diaphragm pump, made using a rubber glove diaphragm and atupperware container.

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Image Notes1. Original Piston Pump prototpe. This featured hand-made (non lasercut) valveswith brass flaps and a dodgy bird mouth joint.

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